tty: synclinkgt: Fix null-pointer-dereference in slgtclean()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v4.19.247 by commit ba08cbc5b53e151d0acf1930fb526fc65b7f3e65. For more details please see the references link.